It is customary in solar heaters and similar devices to use a series of tubes through which a fluid which is to be heated is caused to flow and to interconnect these tubes by means of headers at each end so that a common supply of fluid can be fed to the tubes and after heating can be received from the tubes.
Various forms of construction of such units can be used but it is known to form the tubes through which the fluid flows by extruding plastic materials to produce a unitary cross-section to form what is known as a tube sheet which has a series of tubes placed side by side and generally formed by having an upper wall and a lower wall spaced apart by a plurality of spaced walls to divide the space between the upper and lower walls into a plurality of tubes longitudinally arranged along the unit one form of such is shown in Australian Pat. No. 494,721.
The invention relates generally to a module in which a series of tubes are formed in a single planar element and has a header attached to it at each end to allow fluid which is to pass through the tubes to be fed to the open tubes at one end and to leave the open tubes at the other end, so that one header acts as a supply header and the other as a receiving header for the fluids.
In such a module, a considerable problem exists in joining such headers to the tube sheet which as said contains a series of side-by-side tubes, and it is found in practice that if a header is formed of a plastic material and is joined to the ends of the tube sheet that, when pressure fluid is applied to the system, fracture will occur at the junction between the header and the tube sheet which generally is due to fracturing of the walls of the tube sheet itself at the junction, and consequent failure of the header.
An object of the present invention therefore is to so construct a junction between headers and a tube sheet to minimise the fracture of either the tube sheet or the header.
The term "tube sheet" is intended herein to refer to a substantially planar sheet having an upper and a lower plastic membrane interconnected by a series of spaced division walls which then form a module in which the series of tubes are arranged generally in a flat plane across the module which tubes are continuous through the module and open at the two opposite ends of the module. It is also intended to include a sheet of circular tubes joined in side-by-side relationship.
A further object of the invention is to control the flow of fluid through the tubes of the module because there is normally a tendency in headers which connect such tubes to have a greater flow at some areas, depending on the pressures fluid flow rates, and fluid entrainment effects existing in the headers.
Other objects will be apparent from the following description which is made with reference to specific forms of the invention but it is to be appreciated the invention is not necessarily limited to the forms described.